Turns Vs KV Explained Please?

[nimbuzz]

All this KV and T stuff is driving me crazy--I get 'Turns' but not how it relates to KV. I know KV is RPMs per Volt but then a big 1/8 car will use a low 2000KV motor and it seems if you just geared it higher you'd get more RPMs at the wheels cuz it must have torque so what's up with all that?!?
How to pick a motor?? Turns explains it well to me = I know a stock 17.5 motor is medium fast and go to less Turns it gets faster but uses up the battery quicker. So how can KV be explained in the same terms?
Thanks for info.

 

[kinison]

All this KV and T stuff is driving me crazy--I get 'Turns' but not how it relates to KV. I know KV is RPMs per Volt but then a big 1/8 car will use a low 2000KV motor and it seems if you just geared it higher you'd get more RPMs at the wheels cuz it must have torque so what's up with all that?!?
How to pick a motor?? Turns explains it well to me = I know a stock 17.5 motor is medium fast and go to less Turns it gets faster but uses up the battery quicker. So how can KV be explained in the same terms?
Thanks for info.

KV is the opposite of turns. A higher KV means a faster motor with less torque (like a low turn brushed). Lower KV means more torque but a lower top end (like a high turn brushed). Assuming no change in hearing. From what I've seen it depends on the company but it seems safe to say 3500kv is roughly equal to a 10T. Hope this helps.

 

[xlDooM]

Sounds like you understood just fine. There is no easy rule to convert, nor an easy way to know how fast your vehicle is going to be with a specific motor.

The 1/8 motors tend to be lower KV but they are meant to run on 3s or higher, so they'll end up equally fast (and much more torquey).

To get an idea of the punch a brushless motor is packing, check its max current draw (multiply with 0.67 if it is a 3S rated motor). 25A = stockish, 40A = nicely quick, 60A = whoa.

 

[i_r_beej]

You seem to grasp the concept pretty well, @nimbuzz. I get the idea with "kv" but i find it needlessly confusing since the term means "kilo volts" (kV) in electronics and electrical systems. (True, no RC car will ever run on multiple thousands of volts!) I think RPMV or maybe RV would have been better. But that's beside the point.

Picking a motor is easy. You want speed and power? Look for low turns and a higher "kv" number. Want to pull tree stumps? Look for high turns and a lower "kv" number.

Easy-Peasy.

 

[nimbuzz]

Thanks guys--These all clarify from a different angle!!